LaTeX problem

I have a LaTeX file intended as a submission to an Elsevier
journal, that compiles with a spurious error. A mini-example
is at www.dieterbritz.dk/err.zip. It calls on the file
elsarticle.cls, included. When I compile it with pdflatex,
I get the apparent error

! Missing } inserted.
<inserted text>
                }
l.32 \end{frontmatter}
                     
?

but when I persist, it compiles correctly. So this is
not an error. I can't submit the paper because the journal
will reject it as having an error, so I must fix this.
What is wrong here?
--
db